Any ideas on dimming interior lights

[monkeymagic68]

Hi all
Does anyone have any ideas on interior lighting problem. On the control pannel for the lights, there are three switches, 1 for the awning light which works fine, 2nd switch is for the rear of the van interior lights, they work fine, and the 3rd is for the front of the van interior lights, when pressed the lights go dim and the needle on the battery metre drops to about 7volts im thinking it could be an earthing problem, as if it was shorting, it would blow a fuse, which its not.
Any ideas would be appreciated.

 

[RayS]

I assume all the lights you mention are 12v.
The most likely cause of your problem is, i think, either a bad joint in the wiring or a bad connection in a bulb holder. First step would be to remove each bulb in turn to see if the problem is related to both or only one light. If both, then most likely something in the wiring common to both e.g. the switch. If only one then bulb or bulb holder for that lamp ( or second switch, if lamp fitting also has a switch on it.
If you have a test meter, in the second case try the voltage across the connections to the lamp holder - should be a full 12-13v. Although bulbs usually fail open circuit it is possible for them to have a high resistance joint inside, so test with a spare bulb.

Problem with this sort of fault is that it's easier to fix than describe. The golden rule is only change one thing at a time, then re-test and so on. If it gets complex then write down each step as you go together with result. Sounds very elaborate but it's quicker in the long run.

 

[Robtel]

I've noticed in our van that if someone switches on the toilet lights ( rear toilet/shower with ceiling and under shelf lighting) then the spotlights above the fixed bed dim slightly, all 12v lighting. I always thought it was down to the need for power elsewhere and not enough for full power for everywhere at the one time. As I've said before electricity and I do not get on well so as long as there is some form of lighting I leave well alone.

 

[RayS]

A slight dimming when other lamps are switched on accompanied by a drop of a volt or two on the meter are fairly normal - the wiring size may be a little bit low and/or someone may have changed a bulb for one of a higher wattage than the system was designed for. I suspect that the wiring is designed with a diversification factor built in i.e. not to allow for all lights to be on at the same time without some drop in voltage.
However a drop to about 7 volts is something else.

 

[monkeymagic68]

Thanks Guys
Yes the lights are 12v ive had all the lights disconected out of the fittings with no bulbs in, and it still goes down to about 7volts, i managed to get them working and switched them on and off about 50 times all ok then its gone again im thinking it could be a faulty switch so im going to swap the cables on the good switch to the one thats playing up to see if that helps.